In the broad field of analytical instruments, chromatographs have been used to separate and measure the concentration of the constituents of complex mixtures. In liquid chromatography, an unknown sample is injected into a column having a liquid therein consisting of one or more liquid solvents. A detector at the base of the column detects the presence of the constitutents as they appear or elute from the bottom of the column. A plot of the detector output as a function of time, known as a chromatogram, is used by the chromatographer in his analysis of the unknown sample.
For example, it may be desired to know the concentration of a given medication in the blood stream of a patient. A known volume of blood would be entered into a chromatographic column and the constituent parts including the drug fraction would then separate out and be detected. The chromatogram would indicate the concentration of each component. By knowing when the medication should separate out, the therapeutic drug level of the medication can be determined. From that, the percentage of medication in the blood can be calculated.
The above described instrument and method of operation is very useful when the constituents of the sample are known. However, when the sample is an unknown, the chromatogram produced is more difficult to interpret. In addition, research has shown that the separation of unknowns into their constituent parts in a liquid chromatograph is not always possible with a given multi-solvent column solution. As a result, researchers must vary the concentration of the constituents of the column solution and have used column solutions having 3 or even 4 different constituents. This has improved the capability of the chromatographer to separate more kinds of unknowns into their component parts if a proper column solution can be selected. However, if an improper column solution is used, two or more components may co-elute thereby producing a chromatogram with insufficient resolution. Thus the chromatographer is left with the problem of randomly experimenting with the column solution constituents and evaluating the chromatogram for each such experiment to determine which one is best.
It is the last mentioned task which is very difficult. Typically, a chromatographer may perform a large number of experiments on a given unknown sample, each experiment being done with a different solvent mix in the column. The chromatograph produces a chromatogram from each experiment. For a typical unknown, the chromatographer may perform many experiments before he discovers a set of conditions which are acceptable if not ideal for his purposes. Some of the chromatograms are easily discarded as being unusable but evaluating the remaining chromatograms as to which is the most usable is very difficult. This task becomes more difficult as the number of experiments increases which is necessary when 3 or 4 solvents are used in the column. Without a system and protocol it becomes highly unlikely that an optimum separation will be achieved by trial and error.
It is therefore the primary objective of the present invention to provide a way to assist the chromatographer in selecting the liquid column solvents which will provide a chromatogram with good resolution for a given unknown sample injected into the column.
It is yet another objective of the present invention to provide a way to assist the chromatographer in selecting from a plurality of chromatograms the best chromatogram for use or further evaluation.